Human Nutrition and Respiration: A Comprehensive Guide
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Human Nutrition
The cells of all organisms require nutrients to grow and function. Heterotrophic organisms, like humans, cannot produce their own nutrients, so they obtain them from food. Multicellular organisms have many organs grouped into systems, such as the digestive and respiratory systems.
Digestive System
Like all animals, humans obtain proteins, fats, and sugars from food through the digestive system. Food processing involves three phases: digestion, absorption, and waste expulsion. Food moves through the digestive tract via peristaltic movements—muscle contractions in the tract walls that narrow the tube.
Respiratory System
Besides nutrients from digestion, our cells need oxygen for cellular respiration, the process that converts glucose into energy. This process produces waste products, including carbon dioxide, which must be eliminated. The respiratory system captures oxygen from the air, transfers it to the blood for transport to body cells, collects carbon dioxide from the blood, and expels it from the body.
Components of the Respiratory System
- Airways: Tubes that collect oxygen-containing air, including the nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles.
- Lungs: Where gases (oxygen and carbon dioxide) are exchanged between blood and air.
Respiratory Process
Respiration has two stages: inspiration (inhalation) and expiration (exhalation).
Inspiration (Inhalation)
Air enters and inflates the lungs. Respiratory muscles expand the thoracic cage. The diaphragm contracts and descends, while the ribs lift.
Expiration (Exhalation)
Air leaves the lungs, which relax, and the thoracic cage contracts. The diaphragm relaxes, curves upward, and the ribs move down and in.
Respiratory Rhythm
Respiratory rhythm is the number of inhalations per minute. Normally, it's 12, but it can increase to 40 after strenuous exercise. Around 8 liters of air are moved per minute under normal conditions, increasing to 100 liters during forced breathing.